Experimental studies of the aerodynamics of spinning and stationary footballs

Abstract

The accurate discrimination of the aerodynamic parameters affecting the flight of sports balls is essential in the product development process. Aerodynamic studies reported to date have been limited, primarily because of the inherent difficulty of making accurate measurements on a moving or spinning ball. Manufacturers therefore generally rely on field trials to determine ball performance, but the approach is time-consuming and subject to considerable variability. The current paper describes the development of a method for mounting stationary and spinning footballs in a wind tunnel to enable accurate force data to be obtained. The technique is applied to a number of footballs with differing constructions and the results reported. Significant differences in performance are noted for both stationary and spinning balls and the importance of the ball orientation to the flow is highlighted. To put the aerodynamic data into context the results are applied in a flight model to predict the potential differences in the behaviour of each ball in the air. The aerodynamic differences are shown to have a considerable effect on the flight path and the effect of orientation is shown to be particularly significant when a ball is rotating slowly. Though the techniques reported here are applied to a football they are equally applicable to other ball types.

The application of simulation to the understanding of football flight

“…A comprehensive experimental study of the forces that are generated specifically on footballs can be found in Passmore 6,7 ; drag and lateral force characteristics are reported for spinning and static balls and in the static case the lateral forces are shown to be a function of orientation. Typical Drag coefficient against Reynolds number for a range of footballs is shown in figure 1 along with the results from Achenbach 2 .…”

The aerodynamic performance of a range of FIFA-approved footballs

“…The methods used to derive the data in Figure 12 were based on those reported by Passmore (2), where the ball is tested across a matrix of fixed wind and spin speeds. This is very time consuming to perform and analyse so the spin method has been modified to improve productivity by running at a fixed spin speed while the tunnel speed is reduced from a maximum of 30 ms -1 down to 10 ms -1 .…”

“…This is generally known as the Magnus effect. Given that the player deliberately applies the spin to the ball and the ball will then fly in the same manner every time, this is a predictable effect, however Passmore (2) shows that the degree of swerve in the ball may differ depending on the ball design.…”

Sistema electro-óptico para la medida de los coeficientes aerodinámicos de objetos esféricos en movimiento

“…La Figura 1.11 muestra el túnel con el soporte para las pelotas. El trabajo de Passmore y otros [PTSJ08] con balones de fútbol emplea un túnel de viento de circuito abierto con una sección de 1, 32 × 1,9 m que permite una velocidad máxima de 45 m/s. La medida de las fuerzas se realiza mediante una balanza de 6 ejes de alta precisión diseñada para aplicaciones aeronaúticas permitiendo una resolución de ±0, 012N para arrastre y ±0, 021N para fuerzas laterales.…”

“…La obtención de estos parámetros, para el caso de balones de fútbol, se realiza mediante deferentes técnicas, como ensayos en túneles de viento [ASKS07,PTSJ08] Las Figuras 2.13 y 2.14 muestran los resultados obtenidos en los casos de lanzamientos con rotación y sin rotación respectivamente.…”